Now looking at definitions starting with letter "p"
passband : The passband of a filter is the frequency span that the filter passes, or the range of frequencies not attenuated by the filter. The passband is usually measured between the points where the response is 3dB down in amplitude relative to the maximum level. See rolloff frequency.
passive : A device is called passive if it contains no amplification circuitry and a signal suffers insertion loss in passing through it, i.e., more energy goes into the device than is available at its output. This is opposed to an amplifier or other device which has the potential for at least unity gain. Many audio equalizers are passive, as are most crossover networks. Passive devices in general do not add any appreciable nonlinear distortion or noise to the signal, but they have so much attendant insertion loss that additional amplification is needed, and this always contributes some noise and distortion. Passive devices can and do cause phase distortion, however. As opposed to active.
passive crossover : See crossover network.
passive equalizer : An equalizer that employs only passive electronic components, i.e., resistors, capacitors, and/or inductors. Since these components require voltage, passive equalizers can only cut each operating band, the. The output signal level is necessarilythus lower than the input level. See active equalizer.
patch : (1) (verb) To connect together, as the inputs and outputs of various modules, generally with patch cords. (2) (noun) The configuration of hookups and settings that results from the process of patching, and by extension, the sound that such a configuration creates. Patch is most often used to denote a single sound or the contents of a memory location that contains parameter settings for the sound, even on an instrument that requires no physical patching. A synonym for sample or program.
patch bay : A group of similar receptacles, or jack, in an audio system. The act of plugging and unplugging the patch cords is called patching. Also called a router, jack field, or jack bay. Increasingly, physical patching is being replaced by digital routing.
patch cord : A short cable, typically fitted with a phone plug or TT connector at each end, used to make a connection between two points on a patch bay.
patch map : A map with which any incoming MIDI program change message can be assigned to call up any of an instrumentís patches. This is a table set up by the user with entries such as 1=3, 2=2, 3=984, etc. See patch mapping, MIDI Mapper.
patch mapping : A Program Change message is limited to only 128 values, while some synthesizers can store many thousands of separate patches. This would mean that only 128 of the programs could be accessed via MIDI. Patch mapping is a process whereby a given program change number received by a MIDI device can be linked to any one of the available patches, as determined by a patch map. To get beyond the 128 limit, the MIDI Continuous Controller message, Bank Select, has been defined for selecting different banks of sounds prior to sending a program change number.
patch point : A location in an electronic circuit at which access to the circuit is provided by a jack in the patch bay or console channel strip. See normalled connection, output.
path length : The distance between a sound source and the listener or microphone. See near-field, far-field.
pattern looping : A digital composition technique whereby long, looped samples are mapped into a sampler along with other samples such as bass riffs, drum variations, and solo samples (vocal sounds, effects, etc.) The different loops and solo sounds are brought in and out via a keyboard to create a finished composition.
PCI : Peripheral Component Interface. An internal bus architecture for PCs and the Mac commonly used for digital audio cards.
PCM : Pulse Code Modulation. A technical term for sampling. Any digital method of encoding and decoding the amplitude of an audio signal. For example, an 8-bit PCM yields amplitude values of 0-255, and produces attendant sampling errors and quantization errors. PCM cards are always ROM, and contain only sampled waveforms, contained in a wavetable. See PWM, split-band. See also PAM.
PCM-F1 : A reference to the (discontinued) Sony digital recording system which used an EIAJ-format, 16-bit PCM processor to convert audio into a digital form that can be stored on consumer videotape. The first attempt at digital audio.
PCMCIA personal computer memory card international association. The preferred term is PC Card; a 32-bit implementation is called a cardbus. A credit-card-size interface commonly found in notebook computers. They are primarily used for modems and network interfaces (and storing programs in synthesizers); this specification has historically been inhospitable to audio devices even though a handful of successful advices do exist.
PD : See ProDigital.
PDL : Projectionist Dummy Loader. Union designation for the person in a film recording facility who functions both as projectionist and as a machine room operator.
peak : Peak value is the maximum instantaneous excursion from zero of an audio waveform, as measured by a peak meter (PPM). The peak value of a sound is also the maximum instantaneous pressure excursion of the sound. See crest factor, VU meter.
peak expansion : The adjustment of an expanderís threshold so that most program material passes through unaffected, but peaks or transients are heavily expanded. Used to restore peaks to program material that has been overly compressed.
peak hold : A function of some volume indicators that indicates the peak level of the signal and holds that level until it is either exceeded by a higher peak or the indicator is reset by a time delay or manual reset.
peak level : See peak.
peak-to-peak value : A measure of the highest positive-to-negative voltage swing in any specified segment of the program signal. Twice the absolute value of the greater voltage reached by an adjacent positive or negative transient peak.